The esophageal squamous epithelium has compartments reminiscent of the intestinal epithelium. However, there are striking differences in relationship to the genes that orchestrate the switch from proliferating basal cells to differentiated suprabasal cells in the esophageal epithelium. Eventually, suprabasal cells migrate outward towards the lumen undergoing morphological, biochemical and genetic changes, culminating in desquamated cells that slough into the lumen. The epithelium is continuously renewed. However, given the rapidity of cell turnover, there is susceptibility of the esophageal epithelium to injury by infectious agents and acid reflux, and risk for changes in critical genes that render the epithelium prone to immortalization and malignant transformation. The central hypothesis of this proposal is that epidermal growth factor receptor (EGFR) expression and activation, which is important in the basal cell compartment, is necessary for proliferation but insufficient for transformation due to the upregulation of insulin growth factor binding protein-3 (IGFBP3), which exerts antipreliferative effects and promotes differentiation and senescence. The interplay between EGFR and IGFBP3 is overcome by the abrogation of the p53 and p16/pRb pathways to foster transformation of cells. This hypothesis will be pursued by the following interrelated Specific Aims: (1) To understand the molecular basis of EGFR mediated upregulation of IGFBP3, identified through a gene array comparing primary human esophageal cells (EPC) and EPC retro-virally transduced with EGFR. (2) To elucidate how dominant-negative or mutant p53 cooperates with EGFR through the downregulation of IGFBP3. (3) To understand how the abrogation of the p16/pRb pathway may contribute to transformation in cells that express EGFR and mutant p53. Taken together, the innovative approaches in this proposal will provide new mechanistic insights into the regulation of esophageal epithelial biology, and provide a foundation for understanding key diseases and cancer genetics. The proposed work will be fostered through a carefully designed mentored program, didactic courses, utilization of scientific core facilities, and institutional support. The research will provide a long-term framework for independent investigator status.